pixelmischief Posted February 7, 2021 Share Posted February 7, 2021 I have a busted reset switch. I've desoldered it from the board. Anyone know what connection I need to make between the solder points to get the machine staring up again? Quote Link to comment Share on other sites More sharing options...
pixelmischief Posted February 7, 2021 Author Share Posted February 7, 2021 Here are images of the schematic for the reset button and a picture of the pins that I have soldered in. Can anyone advise me of which pins to connect to which as a bypass for reset button? Quote Link to comment Share on other sites More sharing options...
snarkdluG Posted February 7, 2021 Share Posted February 7, 2021 (edited) The computer will start without it. It is pulled high (+5V) normally without the reset button according to schematics. Then short pin 2 and 3 to reset the computer. Should be the middle pin (common) and the right pin (towards all the resistors). There is also two offset pins but that is just for stability. Or just solder a wire to the middle hole and short that wire to ground when you want to do a reset. Like the outer rim/ground plane that the shielding connects to. Edited February 7, 2021 by snarkdluG Quote Link to comment Share on other sites More sharing options...
pixelmischief Posted February 7, 2021 Author Share Posted February 7, 2021 @snarkdluG So...let me back up a step. When I first got the board, I would power it up and, if on color, show a blank white screen. If on mono, a black screen. I looked around a bit and noticed that reset button was not bouncing back out. When I pulled it out, the machine booted. I removed the reset button and soldered header pins into into the board. I also replaced the memory sockets and changed the TOS ROMS to 2.06; though I have walked the TOS upgrade back now. When I power the machine on now, I get the same behavior I was getting with the stuck reset button and am ASSUMING that I need to jump some connection there to make it work again. Is it possible that the identical behavior is actually being cause by some other problem? How SURE are you that the machine should work fine without a rest button, or did I misunderstand you? Again, thanks for the help. Quote Link to comment Share on other sites More sharing options...
pixelmischief Posted February 7, 2021 Author Share Posted February 7, 2021 @snarkdluG I suppose that the 4th pin - the one on the far right - is that "stability" pin you mentioned. It is not aligned right with the other 3 pins. I assume the solder pad is connected to ground? Quote Link to comment Share on other sites More sharing options...
ParanoidLittleMan Posted February 7, 2021 Share Posted February 7, 2021 Reset button needs to be opened (not short cut) for normal work. Only when is pressed it will give reset signal to CPU and other chips, via that LM chip. So, you need to check with voltmeter, ohmmeter is there shortcut. And voltage on reset line, what is normally high, only low for short time after power on (that's what that LM does) . Quote Link to comment Share on other sites More sharing options...
TGB1718 Posted February 7, 2021 Share Posted February 7, 2021 (edited) 35 minutes ago, pixelmischief said: How SURE are you that the machine should work fine without a rest button, or did I misunderstand you? The reset button when pressed pulls the trigger pin on 1 half of a 556 configured as a monostable multivibrator, to ground, this causes the chip to provide a reset pulse of a defined length to the ST circuits. The reset pin is normally pulled high by R213, so removing the reset button will still allow the machine to boot. I would check you didn't accidentally short any of the pin connections when you put the header back in, for now I would just remove it again and make sure everything works, then as suggested for now 2 wires out the back, one to the centre and the other to the 0V line and touch together when you need to reset. Edited February 7, 2021 by TGB1718 Quote Link to comment Share on other sites More sharing options...
pixelmischief Posted February 7, 2021 Author Share Posted February 7, 2021 Ok. I accidentally happened on something that improves the situation. I power the machine on and get a full "almost white" screen. Then, I connect a jumper wire to header pin 2 (second from the left on the picture of the system board). NOTHING ELSE. I just slip the wire onto the pin. The screen blinks black, goes a slightly brighter white, and boots. @TGB1718 So, you recommend I remove the header pins I soldered in? Is that still your recommendation given the new info? After I remove the pins, what do I have to connect to what? Quote Link to comment Share on other sites More sharing options...
TGB1718 Posted February 7, 2021 Share Posted February 7, 2021 Sounds like just touching the pin (2) is creating enough 'noise' on the pin to cause the 556 to trigger making a 'Reset' happen. If you have a meter, check which of the other pins are connected to R213, that's the other pin that need a wire on it, not too sure why, but it does sound like something is holding the reset pin low during power-on preventing a normal boot to start, or could be R213 is not connected so the trigger pin is 'floating', again check with a meter and have a look at the tracks around the reset button pins to R213. Quote Link to comment Share on other sites More sharing options...
pixelmischief Posted February 7, 2021 Author Share Posted February 7, 2021 I have a working kludge, and the buttons are still available, so I'll order one and replace it. Next... I bought a pair of TOS 2.06 ROMS, but I can't get them to boot. Quick research tells me they should be a drop-in replacement. Is there some other "gotcha" I should look for? Quote Link to comment Share on other sites More sharing options...
TGB1718 Posted February 7, 2021 Share Posted February 7, 2021 (edited) You may need to set/unset some jumpers depending on the ROM's you have, look here https://www.exxoshost.co.uk/forum/viewtopic.php?t=616 bigger pictures here https://www.exxoshost.co.uk/atari/last/tos/index.htm#STE206 Edited February 7, 2021 by TGB1718 Quote Link to comment Share on other sites More sharing options...
pixelmischief Posted February 7, 2021 Author Share Posted February 7, 2021 I already had a set of TOS 2.05's in there. They are also the "long" chips, so no change SHOULD be necessary; at least from what I read. I suspect I may have put them in upside down at some point in this whole journey. Perhaps I fried them. I'll order another set and see how I get on. Quote Link to comment Share on other sites More sharing options...
TGB1718 Posted February 7, 2021 Share Posted February 7, 2021 2 hours ago, pixelmischief said: Perhaps I fried them oops !!! ? Quote Link to comment Share on other sites More sharing options...
+DarkLord Posted February 13, 2021 Share Posted February 13, 2021 (edited) If you're replacing your ROM's then you should go ahead and take it up to TOS v2.06... PS Okay, reading backwards I see you tried some. Still, while you've got your machine open and have the opportunity, I'd take them up to 2.06. Edited February 13, 2021 by DarkLord Additional info... Quote Link to comment Share on other sites More sharing options...
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